Curated Sass Resources

Installing SASS:

http://sass-lang.com/install (Ruby)
https://www.npmjs.com/package/node-sass (C)
https://www.npmjs.com/package/grunt-sass (To use with grunt)
https://github.com/jtangelder/sass-loader (Webpack)

Basics:

http://sass-lang.com/guide

Testing/Sandbox SASS:

http://www.sassmeister.com/

How to structure a SASS project:

http://thesassway.com/beginner/how-to-structure-a-sass-project

SASS Styleguides:

https://css-tricks.com/sass-style-guide/
https://github.com/airbnb/css
http://sass-lang.com/styleguide
http://sass-guidelin.es/

Choose good variable names:

http://thesassway.com/beginner/variable-naming

Difference between mixin, extend, and placeholders:

http://krasimirtsonev.com/blog/article/SASS-mixins-extends-and-placeholders-differences-use-cases

Functions!

http://thesassway.com/advanced/pure-sass-functions
https://www.sitepoint.com/sass-basics-function-directive/

Naming your media queries:

https://css-tricks.com/naming-media-queries/

High level concepts:

http://alistapart.com/article/a-vision-for-our-sass

General Resources:

http://thesassway.com/
https://css-tricks.com/
https://css-tricks.com/snippets/sass/